Assembly to control or govern relative speed of movement between parts

ABSTRACT

Described herein is an assembly and methods of use thereof for controlling or governing the relative speed of motion between the assembly parts via eddy current formation. The assembly and methods also may minimize the number of parts required and may minimize the number of moving parts thereby increasing the mechanical durability of the assembly compared to art designs that may have more moving parts and greater part complexity.

TECHNICAL FIELD

Described herein is an assembly to control or govern relative speed ofmovement between parts. More specifically, described herein is anassembly that uses eddy current formation to control or govern therelative speed of movement between two parts.

BACKGROUND ART

Eddy current formation may be used in a variety of ways to adjust thespeed of rotation of a member. Various apparatus exist, for example inabseiling, to control the descent of a climber or for example, inpersonal protective equipment scenarios to prevent an injury causingfall. Other applications that use eddy current generation are incontrolling payout of line in trains, cable cars, zip line devices androller coasters.

One art device is published as US2012/0055740. This device utilises arotor assembly. The rotors themselves may be conductive or magnetic ormay have conductive or magnetic members attached thereto. When arotational force is applied, the rotors move outwards from a centralaxis via centrifugal force and into a magnetic (or conductive) field. Asthe rotors move through the field, eddy currents are generated, thestrength of which is proportional to the speed of rotation. As the speedof rotation reduces, the rotors are drawn back towards the axis ofrotation via springs. This device is widely used however requires anumber of moving parts. Another disadvantage is that, when the rotorsmove outwards and the field is generated, the magnetic field is notcontinuous around the circumference of the spin axis hence does notprovide a continuous eddy current generation path.

As may be appreciated, reducing the number of parts in mechanicalassemblies may be an advantage so as to reduce assembly cost. Inaddition, moving parts in mechanical assemblies generally require moremaintenance and hence cost more. Minimising the number of moving partsmay be advantageous. Maximising eddy current force generation may alsobe an advantage or at least it may be useful to provide the public witha choice.

Further aspects and advantages of the assembly and methods of usethereof will become apparent from the ensuing description that is givenby way of example only.

SUMMARY

Described herein is an assembly and methods of use thereof forcontrolling or governing the relative speed of motion between theassembly parts via eddy current formation. The assembly and methods mayalso minimise the number of parts required and may minimise the numberof moving parts thereby increasing the mechanical durability of theassembly compared to art designs that may have more moving parts andgreater complexity.

In a first aspect, there is provided an assembly comprising:

-   -   a tube including a wall and void defined therein; and    -   a cylinder that fits into the tube void;    -   wherein, in use, the cylinder and tube have different relative        speeds of rotation to each other and wherein the tube and        cylinder or a part thereof interact to alter an eddy current        induced braking force against different relative speed of motion        with modulation of braking force arising due to a balance of the        forces on the tube and cylinder.

In a second aspect there is provided an assembly substantially asdescribed above wherein the axis and rotation of the tube and/orcylinder is linked to a shaft which may in turn be linked to a spool ofline and wherein the speed control assembly regulates the speed of payout of the line from the spool.

In a third aspect there is provided a method of braking the fall of anobject by the step of linking the object or objects to a spool of linewhich in turn is linked to the assembly substantially as described aboveand allowing the object or objects to fall through gravity therebycreating a torque force on the shaft which in turn causes the speedcontrol assembly to create a braking force on pay out of the line fromthe spool.

In a fourth aspect, there is provided a fall protection safety deviceincluding an assembly substantially as described above.

In a fifth aspect, there is provided an assembly substantially asdescribed above wherein the assembly is incorporated into a zip lineamusement ride to control the acceleration and deceleration of asuspended zip line passenger chair connected to a cable linked with thespeed control system.

The inventor's have devised an apparatus where the various componentsinteract to alter an eddy current induced braking force with modulationof braking force arising due to a balance of the forces on the tube andcylinder determining the extent of force applied.

Advantages of the above include the provision of an assembly and methodwith few moving parts that still provides an efficient use and transferof eddy current forces to control or govern the relative speed ofmovement of parts in the assembly.

BRIEF DESCRIPTION OF THE DRAWINGS

Further aspects of the assembly and methods of use thereof will becomeapparent from the following description that is given by way of exampleonly and with reference to the accompanying drawings in which:

FIG. 1 illustrates a perspective view [FIG. 1A], a side view [FIG. 1B],a front view [FIG. 1C] and a side section view [FIG. 1D] along sectionline AA of one embodiment of the assembly using a lead screw shaft withthe parts in a non-braking alignment;

FIG. 2 illustrates a perspective view [FIG. 2A], a side view [FIG. 2B],a front view [FIG. 2C] and a side section view [FIG. 2D] along sectionline AA of an alternative embodiment of the assembly using a drivingramp on the shaft with the parts in a partial braking alignment;

FIG. 3 illustrates a perspective view [FIG. 3A], a side view [FIG. 3B],a front view [FIG. 3C] and a side section view [FIG. 3D] along sectionline AA of an alternative embodiment of the assembly using a biasmechanism;

FIG. 4 illustrates a perspective view [FIG. 4A], a side view [FIG. 4B],and a front view [FIG. 4C] of an alternative embodiment of the assemblyusing an alternative bias mechanism;

FIG. 5 illustrates a perspective view [FIG. 5A], a side view [FIG. 5B],a front view [FIG. 5C] and a side section view [FIG. 5D] along sectionline AA of an alternative embodiment of the assembly using a drivingramp on the shaft and bias mechanism with the parts in a partial brakingalignment;

FIG. 6 illustrates a perspective view [FIG. 6A], a side view [FIG. 6B],a front view [FIG. 6C] and a side section view [FIG. 6D] along sectionline AA of one embodiment of the assembly using a lead screw shaft and aweight with the parts in a partial braking alignment;

FIG. 7 illustrates a perspective view [FIG. 7A], a side view [FIG. 7B],a front view [FIG. 7C] and a side section view [FIG. 7D] along sectionline AA of one embodiment of the assembly using a lead screw shaft,weight and bias mechanism with the parts in a partial braking alignment;

FIG. 8 illustrates a perspective view [FIG. 8A], a side view [FIG. 8B],a front view [FIG. 8C] and a side section view [FIG. 8D] along sectionline AA of one embodiment of the assembly using a ramp and weightarrangement with the parts in a partial braking alignment;

FIG. 9 illustrates a perspective view [FIG. 9A], a side view [FIG. 9B],a front view [FIG. 9C] and a side section view [FIG. 9D] along sectionline AA of one embodiment of the assembly using a ramp, weightarrangement and bias mechanism with the parts in a partial brakingalignment;

FIG. 10 illustrates alternative shapes of cylinder and tube that may beused;

FIG. 11 illustrates a cross-section side view of a tube and cylinderdesign using multi-layer concentric walls;

FIG. 12 illustrates an alternative cross-section side view embodiment ofa tube and cylinder design using multi-layer concentric walls withvarying magnet positions to that shown in FIG. 11; and,

FIG. 13 illustrates a further cross-section side view multi-layeredconcentric wall embodiment.

DETAILED DESCRIPTION

As noted above, described herein is an assembly and methods of usethereof for controlling or governing the relative speed of motionbetween the assembly parts via eddy current formation. The assembly andmethods also may minimise the number of parts required and may minimisethe number of moving parts thereby increasing the mechanical durabilityof the assembly compared to art designs that may have more moving partsand greater part complexity.

For the purposes of this specification, the term ‘about’ or‘approximately’ and grammatical variations thereof mean a quantity,level, degree, value, number, frequency, percentage, dimension, size,amount, weight or length that varies by as much as 30, 25, 20, 15, 10,9, 8, 7, 6, 5, 4, 3, 2, or 1% to a reference quantity, level, degree,value, number, frequency, percentage, dimension, size, amount, weight orlength.

The term ‘substantially’ or grammatical variations thereof refers to atleast about 50%, for example 75%, 85%, 95% or 98%.

The term ‘comprise’ and grammatical variations thereof shall have aninclusive meaning—i.e. that it will be taken to mean an inclusion of notonly the listed components it directly references, but also othernon-specified components or elements.

The term ‘tube’ and grammatical variations thereof may in one embodimentrefer to a cylindrical element having a circular hole or void that acircular cylinder mates with but also could be a square exterior tubewall and circular void or a polygonal tube wall (interior and exterior)or a frusto-conical tube wall.

The term ‘cylinder’ and grammatical variations thereof may refer tovarious shapes, a key criteria being the ability of the cylinder to moveaxially and/or rotationally relative to the tube void space or viceversa i.e. the tube may also move axially and/or rotationally relativeto the cylinder. Note that the cylinder need not be solid and may have avoid space or spaces therein.

In a first aspect, there is provided an assembly comprising:

-   -   a tube including a wall and void defined therein; and    -   a cylinder that fits into the tube void;    -   wherein, in use, the cylinder and tube have different relative        speeds of rotation to each other and wherein the tube and        cylinder or a part thereof interact to alter an eddy current        induced braking force against different relative speed of motion        with modulation of braking force arising due to a balance of the        forces on the tube and cylinder.

The inventor's have devised an apparatus where the various componentsinteract to alter an eddy current induced braking force with modulationof braking force arising due to a balance of the forces on the tube andcylinder determining the extent of force applied.

The cylinder may move relative to the tube via two separate degrees ofmovement being:

-   -   (a) axial translation of the cylinder relative to the tube so        that the cylinder can pass at least partially into or out of the        tube void; and    -   (b) rotation of the cylinder relative to the tube about a        longitudinal axis, the axis passing through the tube void.

Alternatively, the tube may move relative to the cylinder via twoseparate degrees of movement being:

-   -   (a) axial translation of the tube relative to the cylinder so        that the cylinder can pass at least partially into or out of the        tube void; and    -   (b) rotation of the tube relative to the cylinder about a        longitudinal axis, the axis passing through the tube void.

Coupled to the tube and cylinder may be one or more conductive membersand one or more magnetic members, the tube and cylinder each havingeither magnetic member(s) or conductive member(s) and the conductivemembers and magnetic members orientated to interact with each other.

The tube and cylinder may have a common axis of rotation. As notedabove, the tube and cylinder may have varying cross sectional shapes anddo not need to be circular. It is however anticipated that a circularvoid in the tube and similar mating circular cylinder cross-sectionwould provide the greatest degree of efficiency hence this may beadvantageous for most applications. With two nesting circularcross-sections, a common axis of rotation may be a useful feature.

The cylinder may rotate about a rotating member passing through the axisof rotation of the cylinder and tube. A rotating member may be a shaft,although other configurations may be possible. Other features may beincluded between the shaft and cylinder such as bearings. In analternative embodiment, the tube may rotate about a rotating member suchas a shaft.

The rotating member may include a helical groove in order to translaterotational movement of the member into linear movement of the cylinder.The helical groove pitch and/or lead may be varied in order to vary thebrake response. The rotating member may be a lead screw. A helicalgroove may be used to control and/or drive axial movement of thecylinder. This is not essential as other methods may be used to controland drive axial movement such as different bias arrangements ordifferent bearing face arrangements and a helical groove should not beseen as limiting.

The conductive member or members may be wider than the magnetic memberor members. Whilst not essential, the greatest eddy current generationmay occur when the conductive members are wider than the magneticmembers so that a full-induced magnetic field is generated. Smallerconductive member regions may still be used but a smaller magnetic fieldmay be generated in these circumstances leading to a reduced eddycurrent drag formation.

The gap between the magnetic and conductive members may be minimised inorder to maximise the eddy current brake force. As may be appreciated, alarge gap leads to a smaller magnetic field and less eddy current dragforce generation. This may be advantageous in some circumstanceshowever, to generate the greatest force for the least effort, asubstantially small gap (less than approximately 5 mm, or 4 mm or 3 mm,or 2 mm, or less than 1 mm) may be useful.

The tube may be fixed in place and the cylinder may move axially androtationally relative to the tube. Opposite movement may be useful forexample having the tube move via a motor towards or away from thecylinder but an aim of the assembly described herein is to minimise theoverall number of parts required and also to minimise the number ofmoving parts.

The cylinder may rotate at a different relative speed to the tube in aco-current or counter-current direction. As may be appreciated, of keyimportance to generating eddy currents is a different relativerotational speed between the conductive member and magnetic member. Onemeans of achieving this is to have the conductive member being the tubeand the magnetic member being the cylinder and having each member rotateat a different relative speed. As noted above, the tube may be fixed inplace and not rotate at all. The tube may also rotate in either the samedirection (but at a different speed to the cylinder) or may rotate inthe opposite direction to the cylinder (in which case a stronger eddycurrent force might result due to a greater relative speed difference).

The cylinder may be at least partially outside of the tube when thecylinder and/or tube are not rotating. The cylinder may be at leastpartially inside the tube when the cylinder and/or tube are notrotating. Varying the position of the cylinder axially when the assemblyis at rest may alter the characteristics at start up of rotation. Forexample, if the cylinder is already in the tube, immediate eddy currentdrag force generation will occur when the cylinder (or tube) rotates. Ifthe cylinder is outside the tube when rotation commences, minimalimmediate eddy current force will occur—this delayed effect might beuseful where a small amount of rotation is desired such as when a slowpayout of line is needed in a climbing application. When a fall occurs,the pay out of line becomes much faster and that faster rate of rotationmay then cause engagement of the cylinder and tube via axial translationto generate a drag force and brake effect.

Varying the at least one magnet member strength and/or position on thecylinder or tube may vary the brake response. Varying the at least oneconductive member chemical composition and/or position on the cylinderor tube may vary the brake response. To further illustrate this feature,some art eddy current devices use spaced apart conductive or magneticmembers. The result of this may be a lower level of eddy currentgeneration than a continuous field. For example, the conductivemember(s) may be moving rotationally in and out of a magnetic fieldhence they may only be creating a smaller or less efficient eddy currentdrag force than if the field were continuous. In contrast the describedarrangement of a tube and cylinder means it may be possible to generatea continuous field between the conductive and magnetic members due tothe continuous nature of the tube void surface and cylinder surface. Oneexample of a completely continuous eddy current generating relationshipmay be to have the cylinder made entirely from a conductive member or atleast the outer surface of the cylinder being made from or containing anelectrically conductive member and the tube itself or outer surface ofthe tube void being made from or containing a magnetic member. Acontinuous interface is then created between the two parts for eddycurrent generation. Variations on this may also be undertaken where aless than continuous interface is desired however, the ability to createa continuous surface may be unique and an advantage of this particulardesign.

Varying the relative speed of rotation of the tube and cylinder may varythe brake response. As noted above, relative speed is key in generatingeddy currents. Assuming the axial position of the cylinder and tube doesnot change and the conductive and magnetic members positioning does notchange, a next way of altering the eddy current characteristics may beto change the relative rotation speed.

At least part of the cylinder may contain or may be formed fromelectrically conductive material and may thereby form a conductivemember. At least part of the tube may contain or may be formed fromelectrically conductive material and may thereby form a conductivemember. Conductive members may be placed onto the surface of thecylinder or tube and similarly, magnetic members may be placed on thesurface of the cylinder or tube. The tube or tube void wall may itselfbe a conductor or magnetic material as can the cylinder itself orcylinder exterior.

Axial movement of the tube and/or cylinder may be actuated via at leastone motor. A motor may be avoided to minimise parts and minimise movingparts in the overall assembly although could be incorporated if desired.

The assembly may include a bias member that creates a direct or indirectaxial force on the tube and/or cylinder, biasing the tube and/orcylinder together or apart on rotation of the tube and/or cylinder. Thebias member may be a spring or springs.

Axial movement of the tube and/or cylinder may be generated when thetube and/or cylinder rotates, the axial movement caused by a translationof centrifugal energy into axial translation. The tube and/or cylindermay include at least one weight off-set from the axis of rotation, that,on rotation of the tube and/or cylinder, may be subject a centrifugalforce and, via a kinematic relationship, translates the centrifugalforce into an axial force on the tube and/or cylinder thereby causingrelative axial movement of the tube and/or cylinder. A lever convertingrotational movement of the weight to axial movement of the cylinder ortube may act to form the kinematic relationship. The weight or weightsmay move at least partially radially on application of a centrifugalforce. In an alternative embodiment, centrifugal outward movement of theweight or weights may cause an axial movement of the cylinder by actingon a ramp arrangement.

The tube and/or cylinder may also be formed as multiple layers, thecylinder for example having a hollow interior and mating with a tubethat has outer walls at least partly extending over the outside of thecylinder and internal walls extending into the cylinder hollow interioreither before, during or after relative movement of the tube andcylinder. The tube and cylinder may have multiple nesting concentricwalls. Magnets and/or conductive members may be located on the cylinderwalls and/or one or more of the tube walls (outer and/or inner). In afurther embodiment, the cylinder may have multiple concentric walllayers mating with multiple concentric wall layers on the tube andmagnets and/or conductive members placed on some or all of the walllayers.

In a second aspect there is provided an assembly substantially asdescribed above wherein the axis and rotation of the tube and/orcylinder is linked to a shaft which may in turn be linked to a spool ofline and wherein the speed control assembly regulates the speed of payout of the line from the spool.

The above assembly may include a retraction mechanism that retracts paidout line back onto the spool when a pay out force is removed.

The braking force applied to pay out of the spool of line may be at asubstantially constant speed for extension over a range of appliedtorque.

The assembly as described above may include a housing, the housingenclosing at least a portion of the assembly. A housing may be useful toweather proof the assembly and also to improve the aesthetics of theassembly. A housing may also be important for safety to avoid accidentalinjury.

In a third aspect there is provided a method of braking the fall of anobject by the step of linking the object or objects to a spool of linesubstantially as described above and allowing the object or objects tofall through gravity thereby creating a torque force on the shaft whichin turn causes the speed control assembly to create a braking force onpay out of the line from the spool.

The braking force may also reduce retraction speed of the line enough toallow a fully extended line with nothing attached to the line to cleanlyretract.

The range of applied torque may cover objects attached to the lineweighing about 9, or 10, or 11, or 12, or 13, or 14, or 15, or 20, or25, or 30, or 35, or 40, or 45, or 50, or 55, or 60, or 65, or 70, or75, or 80, or 85, or 90, or 95, or 100, or 105, or 110, or 115, or 120,or 125, or 130, or 135, or 140, or 145, or 150 kilograms. The range maybe from about 9 kg to about 150 kg.

In a fourth aspect, there is provided a fall protection safety deviceincluding an assembly substantially as described above.

In a fifth aspect, there is provided an assembly substantially asdescribed above wherein the assembly is incorporated into a zip lineamusement ride to control the acceleration and deceleration of asuspended zip line passenger chair connected to a cable linked with thespeed control system.

To summarise, control or governance of the relative speed of the membersusing the device described may occur as per the two examples A and Bbelow:

-   [A] In the embodiment of a cylinder interacting with a shaft and    tube where:    -   The two are connected in a manner wherein a kinematic        relationship exists where relative rotation of the two along        their axis is linked to a corresponding relative translational        motion;    -   Application of a torque on the shaft causes rotation of the        shaft and thereby rotation of the cylinder;    -   Rotation of the cylinder results in formation of a eddy current        drag torque on the cylinder; and/or    -   An inertial torque is generated by the cylinder due to an        applied rotational acceleration of the shaft;    -   The kinematic relationship provides a corresponding axial force        on the cylinder;    -   A biasing device may be connected between the shaft and cylinder        whereby the bias is in relationship with the relative rotation        of the shaft and cylinder, and the relative rotation of the        cylinder and shaft reaches an equilibrium where the eddy drag        torque and the inertial torque are balanced by the reaction        torque of the bias device; or    -   A biasing device is connected between the cylinder and a        ‘ground’ body (possibly the tube or support structure), whereby        the bias is in relationship with the relative translation of the        shaft and cylinder, and the relative translation of the cylinder        and shaft reaches an equilibrium where the induced axial force        induced by the kinematic connection of the eddy drag torque and        the inertial torque are balanced by the axial reaction force of        the bias device; and    -   The resulting equilibrium position of the shaft, cylinder, and        tube provide a controlled eddy current induced braking torque        based on the rotational speed and acceleration of the shaft; and    -   The induced torque balances an applied torque.-   [B] A cylinder interacting with a shaft wherein    -   The two are connected in a manner wherein a kinematic        relationship exists where relative translational motion is        allowed and a centrifugal system is arranged to apply axial        force on the cylinder upon rotation of the shaft; and    -   A biasing device is connected between the cylinder and a        ‘ground’ body (possibly the tube or support structure), whereby        the bias is in relationship with the relative translation of the        shaft and cylinder, and the relative translation of the cylinder        and shaft reaches an equilibrium where the centrifugally induced        axial force is balanced by the axial reaction force of the bias        device; and    -   The resulting equilibrium position of the shaft, cylinder, and        tube provide a controlled eddy current induced braking torque        based on the rotational speed and acceleration of the shaft; and    -   The induced torque balances an applied torque.

Advantages of the above assembly include the ability to control orgovern relative speed of motion between the parts in an efficient mannerthat may also minimise the number of parts required and may minimise thenumber of moving parts. Reducing the number of moving parts may increasethe mechanical durability of the assembly since typically in mechanicaldevices, moving parts are where mechanical objects either fail orrequire maintenance (and hence cost more).

The embodiments described above may also be said broadly to consist inthe parts, elements and features referred to or indicated in thespecification of the application, individually or collectively, and anyor all combinations of any two or more said parts, elements or features,and where specific integers are mentioned herein which have knownequivalents in the art to which the embodiments relates, such knownequivalents are deemed to be incorporated herein as of individually setforth,

Where specific integers are mentioned herein which have knownequivalents in the art to which this invention relates, such knownequivalents are deemed to be incorporated herein as if individually setforth.

WORKING EXAMPLES

The above described assembly and methods of use are now described byreference to specific examples.

Example 1

Referring to FIGS. 1A-1D, one embodiment of the assembly is shown. Theassembly 1 as illustrated includes a tube 2 with an inner 3A and outerwall 3B and a void 4 therein. The assembly 1 also includes a cylinder 5.The cylinder 5 moves relative to the tube 2 via two degrees of movementbeing an axial translation along arrow A into and out of the tube 2 void4 and a rotational movement B relative to tube 2. Axial movement A canbe completely or partially into or out of the void 4. In the embodimentillustrated, the tube 2 and cylinder 5 share a common central axis ofrotation. The cylinder 5 may rotate in direction B about a shaft 7. Theshaft 7 may have a helical groove thereon which, when the shaft 7rotates in direction B, drives axial movement A of the cylinder 5relative to the tube 2. The tube 2 and cylinder 5 may include one ormore conductive members and magnetic members (not shown). In oneembodiment, the conductive member(s) may be on the tube 2 or the tube 2it self may be a conductive member and the magnetic member(s) may be onthe cylinder 5 or the cylinder 5 itself may be a magnetic member. Theopposite scenario may also be the case with the conductive member(s) onthe cylinder 5 or the cylinder 5 it self may be a conductive member andthe magnetic member(s) may be on the tube 2 or the tube 2 it self may bea magnetic member. In use, when the tube 2 and cylinder 5 have differentrelative speeds of rotation, eddy current drag forces are producedbetween the members 2, 5 resisting rotation when placed in closeproximity. In one embodiment, the tube 2 may be fixed in position andthe cylinder 5 rotates. When the cylinder 5 enters the tube 2, eddycurrent forces (not shown) create a drag force on rotation B of thecylinder 5 and the speed of rotation B reduces. As may be appreciated,an eddy current force does not necessarily stop all rotation B butarrests speed of rotation to a level related to the relative magneticfield produced by movement of the cylinder 5 in the tube 2 void 4. Fastrelative rotational movement B may result in a strong brake force forexample. In other embodiments, the tube 2 may also rotate in the samedirection as the cylinder 5 (but at a different relative speed) or in acounter rotational direction to the cylinder 5.

A noted above, the shaft 7 may have a helical groove driving axialmovement of the cylinder 5. The helical groove may be a thread or may bea lead screw. The helical groove pitch and/or lead may be varied inorder to vary the brake response. By way of example, the pitch and/orlead may be such that a small rotation of the shaft 7 causes a largeaxial translation A of the cylinder 5 leading to a quick braking forcebeing applied as the cylinder 5 moves quickly into the tube 2 and aneddy current force is generated. The opposite may also be the case wherepitch/lead is varied to only allow a slow axial A progression, thereforeresulting in a slow braking response.

FIGS. 2A to 2D illustrate an alternative embodiment where axial movementof the cylinder 5 may be driven by a ramped surface 16 about aninterface 13 in the cylinder 5. As the cylinder rotates 5, the cylinder5 is forced into the void 4 of the tube 2. In this example, no helicalthread is required on the shaft 7 in order to drive movement.

FIGS. 3A to 3D illustrate an alternative embodiment where axial movementof the cylinder 5 may be influenced also by a bias mechanism such as aspring 8. The spring 8 may be used to change the characteristics of thebraking action. For example, the spring 8 may be biased to draw thecylinder 5 out of the tube 2. When rotation of the cylinder 5 slowssufficiently, the spring 8 in this embodiment may act to draw thecylinder 5 from the tube 2 and thus release the braking force. In analternative embodiment, the spring 8 may be used instead to force thecylinder 5 into the tube 2 to maintain a braking force for a longerperiod of time or to speed the pace within which a braking force may beapplied.

FIGS. 4A to 4C illustrate a further alternative biasing arrangement. Thecylinder 5 in the assembly 1 shown may be attached to a bar or fixedcylinder section 18 with each distil end of the section 18 connected totwo sides of the cylinder 5 via two bias members 23, 24. The connectionpoints of the spring members on the cylinder 5 are offset relative tothe connection points on the bar 18. When the cylinder 5 rotates, theoffset reduces or disappears entirely effectively lengthening thedistance between the bar 18 and cylinder 5 and forcing the cylinder 5into the void 4. When rotation B slows or stops, the bias members 23, 24draw the cylinder 5 back towards the bar 18 and to the offset at restposition.

FIGS. 5A to 5D show how the embodiment shown in FIGS. 2A to 2D may becombined with a bias such as a spring 8 to combine the effects of both aramped 13 axial A displacement and a bias 8 axial A displacement.

FIGS. 6A to 6D illustrate how a centrifugal force component may also beused to change the characteristics of the assembly 1. In the exampleshown, a weight 11 may be connected to the cylinder 5. When the cylinder5 rotates, the weight 11 also rotates and a centrifugal force acts onthe weight in direction F. Via a kinematic relationship, centrifugalforce F on the weight 11 may be translated into an axial force A on thecylinder 5 to push (or pull) the cylinder 5 into or out of the tube 2.The kinematic relationship may be via a lever arrangement 12. This meansof adjusting the characteristics may be useful in certain embodiments.

Also as shown in FIGS. 6A to 6D, the shaft 7 may be attached to a spool9 of line to which an object (not shown) such as a person may beattached. As a force is applied on the line and spool 9 in direction Xsuch as the object falling due to gravity, line is paid out from thespool 9 causing rotation of the spool 9 and shaft 7 in direction Bleading to the cylinder 5 moving into or away from the tube 2 void 4. Byway of example, a person may be the object which falls from a height.Through gravity the spool 9 rotates as line is paid out from the spool9. Rotation of the spool 9 causes rotation of the shaft 7 that in turncauses the cylinder 5 to enter the tube 2 void 4 that may be fixed inposition. The differing rotational speeds of the tube 2 and cylinder 5cause an eddy current drag force (not shown) to occur which therebyslows the fall of the person on the line.

FIGS. 7A to 7D illustrates the same centrifugal arrangement as in FIGS.6A to 6D however with the inclusion of a bias 8 to assist with drawingin or forcing out the cylinder 5 from the tube 2 void 4.

FIGS. 8A to 8D illustrate an alternative method of forcing axialtranslation A to the cylinder 5 using both centrifugal force and a rampmethod. When the shaft 7 rotates, the weight(s) 15 are forced to moveoutward in direction F thereby acting on the ramp surface 16 of thecylinder 5 causing an axial translation A of the cylinder 5. As rotationspeed B decreases, the centrifugal force F acting on the weights 15decrease and the cylinder 5 returns to a non-retracted position.

FIGS. 9A to 9D illustrate the same embodiment as in FIGS. 8A to 8D wherea bias spring 8 is also used to change the axial movement Acharacteristics of the cylinder 5 into or out of the tube 2 void 4.

FIG. 10 illustrates some further alternative tube 2 and cylinder 5arrangements. The embodiments described above utilise a circular tube 2with a circular void but the tube 2 may have any polygonal exteriorshape such as a square shape. The tube 2 internal void shape may becircular as shown in earlier Figures could also be elliptical, square,hexagonal and so on. Similarly, earlier Figures show a circularcross-section cylinder 5 but the cylinder 5 may take various shapes andmay also be hollow.

Example 2

A multilayer wall approach may also be used.

As shown in FIGS. 11 to 13, the cylinder 50 is hollow 51 and mates witha tube 60 that has a complimentary hollow 61. The overlapping walls 52,62 of the cylinder and tube may contain magnets and/or conductivemembers that allow variation in eddy current tuning to occur. FIGS. 11and 12 illustrate a multilayer tube 60 nesting with a hollowed cylinder50 and two alternate magnet 63 configurations on the tube walls 62. FIG.13 illustrates a multiwall 52, 62 approach where both tube 60 andcylinder 50 have multiple concentric walls 52, 62 that mate together.

Aspects of the assembly and methods of use have been described by way ofexample only and it should be appreciated that modifications andadditions may be made thereto without departing from the scope of theclaims herein.

What is claimed is:
 1. An assembly comprising: a tube including an inner and outer wall and void defined therein; and a cylinder that fits into the tube void, the tube and cylinder, wherein one of the cylinder and tube moves relative to the other of the cylinder and tube via two separate degrees of movement being: axial translation of one of the cylinder and tube relative to the other of the cylinder and tube so that the cylinder can pass at least partially into or out of the tube void; and rotation of one of the cylinder and tube relative to the other of the cylinder and tube about a longitudinal axis, the longitudinal axis passing through the tube void; and the tube and cylinder are connected in a manner where a kinematic relationship exists between the tube and cylinder where relative rotation of the tube and cylinder along their axes is linked to a corresponding relative translational motion along the longitudinal axis passing though the tube and void, wherein the cylinder rotates about a shaft passing through the longitudinal axis of the cylinder and tube, and wherein the shaft has a helical groove and/or ramped surface that urges axial movement of the tube and cylinder together or apart about the longitudinal axis when the tube and cylinder have different relative speeds of rotation; and coupled to the tube and cylinder are one or more conductive members and one or more magnetic members, or the tube and/or cylinder themselves being magnetic or conductive members, the conductive members and magnetic members or portions thereof orientated to be less than 5 mm apart when aligned so as to interact with each other so that; when the cylinder and tube one or more conductive members and one or more magnetic members have different relative speeds of rotation to each other, the one or more one or more conductive members and one or more magnetic members interact inducing an eddy current braking force against different relative speed of motion of the tube and cylinder with a modulation of braking force arising due to a balance of the forces on the tube and cylinder caused by both rotational movement and axial movement of the tube and cylinder along the longitudinal axis to an equilibrium position of the tube and cylinder axially and rotationally to provide a controlled eddy current induced braking torque.
 2. The assembly as claimed in claim 1 wherein the tube and/or cylinder is linked to a shaft which is in turn linked to a spool of line to which an object is attached and, as force is applied on the line and spool, line is paid out from the spool causing rotation of the spool and shaft leading to the cylinder moving into or away from the tube void, the differing rotational speed and axial translation of the tube relative to the cylinder causing an eddy current drag force to occur which thereby slows pay out of the line from the spool.
 3. The assembly as claimed in claim 2 wherein the braking force applied to pay out of the spool of line is at a substantially constant speed for extension over a range of applied torque, the range of applied torque covering objects attached to the line weighing 9 to 150 kilograms.
 4. The assembly as claimed in claim 1 wherein the tube and cylinder have a common longitudinal axis of rotation.
 5. The assembly as claimed in claim 1 wherein the conductive member or members are wider than the magnetic member or members.
 6. The assembly as claimed in claim 1 wherein the tube is fixed in place and the cylinder moves axially and rotationally relative to the tube.
 7. The assembly as claimed in claim 1 wherein the cylinder is fixed in place and the tube moves axially and rotationally relative to the cylinder.
 8. The assembly as claimed in claim 1 wherein the cylinder and tube rotate at a different relative speeds in a co-current or counter-current direction.
 9. The assembly as claimed in claim 1 wherein the cylinder and tube are at least partially separate when the cylinder and/or tube are not rotating.
 10. The assembly as claimed in claim 1 wherein the cylinder is at least partially inside the tube when the cylinder and/or tube are not rotating.
 11. The assembly as claimed in claim 1 wherein at least part of the cylinder contains or is formed from electrically conductive material and thereby itself forms a conductive member.
 12. The assembly as claimed in claim 1 wherein at least part of the tube contains or is formed from electrically conductive material and thereby itself forms a conductive member.
 13. The assembly as claimed in claim 1 wherein the assembly includes a bias member that creates a direct or indirect axial force on the tube and/or cylinder, biasing the tube and/or cylinder axially together or apart on rotation of the tube and/or cylinder when the tube and cylinder have different relative speeds of rotation.
 14. The assembly as claimed in claim 1 wherein axial movement of the tube and/or cylinder is caused by a translation of centrifugal energy into axial translation when the tube and cylinder have different relative speeds of rotation.
 15. The assembly as claimed in claim 1 wherein the assembly includes a housing, the housing enclosing at least a portion of the assembly.
 16. A fall protection safety device including an assembly as claimed in claim
 1. 17. A zip line amusement ride to control the acceleration and deceleration of a suspended zip line passenger chair, comprising an assembly as claimed in claim
 1. 18. The assembly as claimed in claim 1 wherein a continuous eddy current generating relationship exists with the cylinder being made entirely from a conductive member or at least the outer surface of the cylinder being made entirely from or containing a conductive member and/or the tube itself or outer surface of the tube void being made from or containing one or more magnetic members. 